There is a technology for, when a child becomes lost, supporting a search for the lost child by use of a mobile phone. For example, Patent Literature 1 discloses a method for supporting a lost child by causing a lost-child candidate and his/her guardian, who are visitors, to carry a lost-child emblem in which information is recorded in advance, reading the information of the lost-child emblem with a mobile terminal carried by on-site staff and/or the guardian when the child becomes lost, transmitting lost-child protection information and/or a lost-child notice to a management server via email, sending and receiving an email between the management server and the mobile terminal, and searching for and protecting the lost child.